This study examined the efficacy of a couple-focused group intervention on psychological adaptation of women with early stage breast cancer and evaluated whether perceived partner unsupportive behavior or patient functional impairment moderated intervention effects. Two hundred thirty-eight women were randomly assigned to receive either 6 sessions of a couple-focused group intervention or usual care. Intent-to-treat growth curve analyses indicated that participants assigned to the couples' group reported lower depressive symptoms. Women rating their partners as more unsupportive benefited more from the intervention than did women with less unsupportive partners, and women with more physical impairment benefited more from the intervention group than did women with less impairment. Subgroup analyses comparing women attending the couple-focused group intervention with women not attending groups and with usual care participants indicated that women attending sessions reported significantly less distress than did women receiving usual care and women who dropped out of the intervention.